Many movie-goers know Tom Hanks played Forest Gump to a man stranded on an island with a volleyball in “Cast Away,” but what many people didn’t know until a recent appearance on "Late Show With David Letterman" was that the actor suffers from Type 2 diabetes.

"I went to the doctor and he said, 'You know those high blood sugar numbers you've been dealing with since you were 36? Well, you've graduated,' " Hanks told Letterman while promoting his film, "Captain Phillips." " 'You've got Type 2 diabetes, young man.' "

Several patients who come to us at DM Foot and Ankle in Lemont, Ill. suffer from Type 2 diabetes. It's a disease where the body either does not produce enough of the hormone insulin to function properly, or the body’s cells don’t respond to insulin that’s there, resulting in poor blood sugar control. The Centers for Disease Control and Prevention says roughly 26 million Americans-- 8.3 percent of the population – have diabetes.

Weight is often a factor. According to cnn.com, Hanks’ weight has gone up and down for movie roles. He reportedly gained 30 pounds to play a cranky, WWII-era baseball coach in "A League of Their Own,” then lost 50 pounds years later for "Cast Away." Other factors are family history, increased fat in the stomach region, lack of exercise, age, and certain races including black, Hispanic, Asian, or of American Indian descent.

Peripheral Neuropathy: This occurs when the small fiber nerves of the feet become damaged, which can cause numbness, tingling, pain, and imbalance. The inability to feel is dangerous – some people may step on a nail and not feel it go through their foot.

Skin Changes: Skin can become discolored or very dry and cracked. One may become more prone to calluses. Proper skin care is necessary to help reduce cuts or open sores.

Poor Circulation: Diabetes causes blood vessels to narrow and harden. This causes reduced blood flow to the feet, reducing healing potential and oxygen to the tissues.

Combined, these factors can lead to open sores, falls, or even amputation. The good news is that diabetes can be managed through medication, insulin, proper diet, exercise and weight control. Diabetes who see a podiatrist are much less likely to suffer from hospitalization and amputations. The American Diabetic Association recommends yearly foot exams. Medicare and other insurance companies also offer coverage for diabetic shoes and inserts yearly.

During his time on Letterman, Hanks joked that he can't follow his doctor's advice to return to his high school weight -- 96 pounds -- to control his diabetes.

"And I said to (the doctor), 'Well I'm gonna have Type 2 diabetes,' " Hanks joked.